This invention relates to cutting inserts for rotary cutting tools, and, more particularly, indexable cutting inserts for rotary cutting tools such as milling cutters having helically arranged teeth.
For illustrative purposes, this specification will describe the invention as it pertains to a conventional milling cutter,. i.e., a milling cutter having a shank portion and a cutting portion of cylindrical configuration, the cutting portion containing a plurality of helically disposed gullets extending from the shank end of the cutting portion to the free end thereof, which gullets define a plurality of helically arranged teeth. In such a milling cutter, the cutting edges, which comprise the leading edges of the teeth defined by the gullets, lie on a substantially constant radius with respect to the longitudinal axis of the tool, throughout the length of the cutting portion. However, the invention may have application to other types of milling cutters, and other types of cutting tools which have helically arranged teeth and which utilize replaceable cutting inserts.
In a conventional rotary cutting tool wherein the teeth and cutting edges are integral with the tool body, the cutting edges of the teeth may be sharpened, within defined limits. However, generally speaking when the cutting edges become worn or damaged beyond restoration, the entire tool must be discarded, and, as such tools conventionally comprise very expensive high performance cutting steels, the replacement of such tools entails considerable expense.
Accordingly, replaceable cutting inserts are frequently mounted on tool bodies in such a manner that the inserts are readily replaceable, and are so disposed along the teeth of the cutting tool that they comprise the cutting edges of the teeth. In this way, the cutting tool may be composed of a lesser quality steel, and only the cutting inserts may be composed of hard wear resistant material, suitable for metal cutting applications, such as hardened tungsten carbide. The cost of the tool itself may therefore be reduced and if the cutting edge, or portions of the cutting edge of the tool becomes subject to damage or excessive wear, it is only necessary to replace the inserts, or some of the inserts, to restore the cutting edge. This can frequently be accomplished with relative simplicity in a few minutes. Indeed, in many cases the cutting inserts are indexable, in the sense that they comprise two or more essentially identical cutting edges, and it is only necessary to remove the insert and rotate it to appropriately introduce a new cutting edge into position in order to renew a damaged or excessively worn cutting edge or a portion of the cutting edge.